Developing the Atomic Theory

Aristotle

300

Aristotle believed in four elements, air, water, fire and earth. he believed that no matter how many times you cut something in half, you still get a smaller peice of that matter.

Arostotle's Atomic Model

300

Democritus

400

Around 400 B.C.E, a scientist named Democritus believed that if you keep cutting something in half it becomes an atom. He proposed that these tiny particales called atoms, make up all matter everywhere.

Democritus's model

400

John Dalton

Dec 21, 1803

In 1803 scientist John Dalton reintroduces the concept of atoms that Democritus made with with actual evidence to support his claims and ideas.

Dalton's Atomic Model

Dec 21, 1803

J.J Thomson

Dec 21, 1897

In a 1897, J.J Thomson he identified particles that are present in every single atom.

Thomson's Atomic Model

Dec 21, 1897

Millikan's Atomic Model

Sep 28, 1909

Robert Millikan

Dec 21, 1909

In 1909 Robert Millikan determined the unit charge of the electron.

Ernest Rutherford

Dec 21, 1911

In 1911 Ernest Rutherford discovered the positivley charged nucleus of an atom.

Rutherford's Atomic Model

Dec 21, 1911

Neils Bohr

Dec 21, 1913

Neils Bohr discovered in 1913 that electrons move about the nucleus in paths.

Bohr's Atomic Model

Dec 21, 1913

James Chadwick

Dec 21, 1932

James Chadwick discovered the neutron in 1932.

Chadwick's Atomic Model

Dec 21, 1932